Abstract: The exposed carbonate limestone area at Guilin has red clay of high plastic limit. The clay was formed by laterization from limestone. Its pores are large and have high water contents It has the character of strong two layer structure. The upper layer is hard and the lower layer is soft. The upper clay has the rigid and hard plastic condition and high bearing capacity. The lower clay is soft plastic, has flowing plastic condition and weak bearing capacity. It needs treatment. This papers uses the soil-cement mixing method to treat the soft red clay. Laboratory tests are done on the mechanical properties of the cemented soils. The test results include the deformation of character and strength of the cemented clays taking into account the effects of cement-soil ratio and age.